The present invention relates to a fuel injection control apparatus for use in an engine and, more particularly, it relates to an improvement of the fuel injection control means which controls fuel to be injected in a controlled amount to each cylinder of the internal combustion engine, namely, a diesel engine.
The fuel injection system is intended to control fuel to be injected to each of its cylinders with every injection and in the case of this fuel injection system, the injection timing is obtained by the mechanical cam system whose rotation is controlled depending upon the engine rotation. In addition, the fuel injection timing is controlled by opening and closing the high pressure fuel passage by means of the electronically-controlled electromagnetic valve.
The fuel injection control means of this type, however, makes it necessary to control the injection timing depending upon the number of engine rotations and load conditions, thereby becoming complicated, large-sized and expensive.
In the engine test carried out under high pressure fuel injection using the unit injector, however, it has been found that the optimum point for engine output, fuel consumption cost, exhausted gas and the like doesn't depend upon the number of engine rotations but the injection timing. More specifically, it is unnecessary, under high pressure fuel injection for the fuel injection timing to be changed corresponding to the number of engine rotations. Therefore in the unit injector, the fuel injection timing is not related to the number of engine rotations but it may only be controlled by load conditions.